Such a heat exchanger unit is known, for example, from DE 10 2012 220 792 A1. This heat exchanger unit comprises a pot-like heat exchanger housing with a circumferential wall and with a bottom wall as well as a pot-like inner heat exchanger housing inserted into the outer heat exchanger housing with a circumferential wall and with a bottom wall. A heat transfer medium flow space for liquid heat transfer medium to be heated is formed between the two heat exchanger housings. A heat transfer medium inlet opening as well as a heat transfer medium outlet opening are formed in a housing inlet pipe and in a housing outlet pipe, respectively, on the circumferential wall of the outer heat exchanger housing. The housing inlet pipe and the housing outlet pipe are located, relative to a housing longitudinal axis, in the same length range, i.e., they have the same axial distance from the bottom wall of the outer heat exchanger housing, and are located parallel next to each other in the circumferential direction, so that the openings formed therein have mutually parallel opening longitudinal axes.
To integrate such a heat exchanger unit in the heat transfer medium circuit, lines configured, for example, in the manner of flexible tubes are pushed over the pipes formed on the housing and are fixed thereon by tube clamps or the like.